Microsoft released an emergency software fix after it learned that hackers had exploited a previously undiscovered security flaw in its Office software and could infect the PCs with tainted Word documents.

Redmond said that it had released the software, known as a "Fix It," as a temporary measure until it provides an update that will automatically patch computers to protect against the new threat. A “very limited" number of attacks that exploited the newly discovered vulnerability, mainly in the Middle East and South Asia. Victims received emails asking them to open the tainted Word documents.

The vulnerability affects customers using Office 2003 and Office 2007 as well as those running Office 2010 on Windows XP and Server 2003.